A collimator is a device which changes the direction of light received by the collimator such that light emitted from the collimator is aligned in a specific direction. Consequently, light with a certain angular range entering the collimator may be emitted with a narrower angular range, i.e. emitted light is collimated (paralleled). The collimator may comprise a total inner reflection (TIR) surface such that the light losses in the collimator are largely avoided.
A problem with collimators may be that the colour and light mixing properties of the collimator is not sufficient such that light emitted from the collimator for example may contain darker areas and lighter areas or the colour homogeneity of emitted light may be unsatisfactory. One solution to this problem may be to include facets on the TIR surface or lenticular lens arrays on the light exit surface of the collimator.
WO 2006/033032 A1 (Koninklijke Philips Electronics N.V.) discloses a combination of a facetted light collimator and a facetted light reflector. The facetted light collimator comprises facets in different levels. The document further discloses a light-shaping diffuser positioned such that emitted light from the facetted light collimator is diffused by the diffuser.
WO 2013/029400 (Huizhou light engine LTD) relates to a lens applied to semiconductor solid-state lighting comprises a lens body; a total reflection surface disposed on an outer side of the lens body, the shape of the total reflection surface being a scaly polyhedron; a recess, formed in a middle position below the lens body, and used for accommodating an LED, the recess having a side surface and a top portion, and the side surface of the recess being in the shape of a cylindrical surface, a tapered surface or a revolution surface; a micro-lens array formed at the top portion of the recess; and an exit surface disposed at the top portion of the lens body, the exit surface comprising one or more flat or curved surfaces.
However, further improvements of the light mixing and colour mixing properties of a collimator are desired.